The present invention relates to epoxy-functional polymeric microbeads that may be prepared by suspension polymerization.
Several methods for the preparation of polymeric microbeads for chromatographic separations have been developed over the past several decades. Typically, these methods involve the free radical suspension polymerization of a mono- and a difunctional vinyl monomer in water. In addition, if a high surface area is desired, macroporous beads with a large internal pore structure can be produced by the incorporation of a porogen consisting of a solvent or a polymer or a mixture of both. Typically, these techniques result in the formation of microbeads with a wide distribution of sizes. Recently, there has been much activity in this field directed towards the generation of functionallized macroporous microbeads for chromatographic separations of specific compounds and for the separation of chiral compounds. This field is highly active at the present time and the chief goal is to prepare macroporous microbeads to efficiently achieve the above separations in the pharmaceutical industry.
Ultraviolet curable monomers are of increasing current interest for such applications as coatings, inks, adhesives and composites because they provide materials which are ecologically attractive. Such monomers are typically employed without the use of solvents and are very efficiently converted to polymers in a very short time during polymerization resulting in no environmental consequences for either water or air pollution. The use of such chemistry for the preparation of functionallized macroporous microbeads has not been described. In particular, the use of the photoinitiated cationic polymerization of epoxide monomers for this purpose has not been reported.
In one aspect, the present invention relates to a population of polymeric microbeads bearing epoxy functionality on surfaces thereof and having a narrow particle size distribution, such that the particle size of greater than 90% of the polymeric microbeads in said population is equal toxc2x120% of the mean particle size. In a preferred embodiment.the epoxy functionality arises from one or more multifunctional epoxy monomers chosen from the group consisting of: 3,4-epoxycyclohexyl methyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate, bis-(3,4-epoxycyclohexyl), adipate, 4-vinylcyclohexene dioxide, epoxy silicone resins, limonene dioxide, dicyclopentadiene dioxide, bisphenol-A diglycidyl ether, bisphenol-F diglycidyl ether, 1,4-butanediol diglycidyl ether, diglycidyl ethers of tetrabromo-bisphenol-A, epoxy cresol novolacs, epoxy phenol novolacs, and diglycidyl phthalate. More preferably, the epoxy functionality arises from one or more multifunctional epoxy monomers chosen from the group consisting of: 3,4-epoxycyclohexyl methyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate, 4-vinylcyclohexene dioxide and the compounds of formula I and II: 
The polymeric microbeads may derived from the copolymerization of one or more multifunctional epoxy monomers and one or more cationically polymerizible comonomers. Preferably, the cationically polymerizible comonomers are chosen from the group consisting of: 1,2-epoxytetradecane, 1,2-epoxydecane, 1,2-epoxydodecane, epoxidized soybean oil, epoxidized linseed oil, vinyl ethers, 1-propenyl ethers, 1-butenyl ethers, styrene, indene, acenapthalene, a-methylstyrene, N-vinyl carbazole, oxazoline, tetrahydrofuran, 7-oxabicyclo[2.2.1]heptane, oxetane, substituted oxetanes, thirane, and aziridine.
In another aspect, the present invention relates to polymeric microbeads prepared by suspension photopolymerization of one or more multifunctional epoxy monomers. Preferably, the dispersion comprises a non-aqueous suspending medium. Polymerization is initiated by a cationic photoinitator.
In yet another aspect, the invention relates to a dispersion of polymeric microbeads prepared by suspension photopolymerization of one or more multifunctional epoxy monomers. Preferably, the multifunctional epoxy monomers are copolymerized with one or more cationically polymerizible comonomers.
In yet another embodiment, the present invention relates to a process for the preparation of polymeric microbeads comprising:
(A) forming a dispersion comprising one or more multifunctional epoxy monomers in a non-aqueous suspending medium in the presence of a photoinitiator; and
(B) exposing the dispersion to a source of light to induce polymerization.
In yet another aspect, the present invention relates to a method for attaching functional groups.to the surface of a polymeric microbead comprising:
(A) preparing a dispersion of polymeric microbeads bearing residual epoxy groups on surfaces as described above and
(B) contacting the polymeric microbeads with a compound which is reactive toward the residual epoxy groups.